EVALUATION OF MODELS FOR SIZE-EXCLUSION CHROMATOGRAPHY OF ASYMMETRIC SOLUTES

We consider two presentations regarding the size exclusion chromatography of highly asymmetric solutes: one is embodied in the statistical model of Giddings et al.; the second is described by the concept of ''end-on insertion'' proposed by Tanford and expanded upon by Meredith and Nathans. Our evaluation is based on measurements of K-sec for the rigid rodlike and spherical solutes schizophyllan and ficoll, respectively, and also on measurements of the experimental flow rate dependence of K-sec. The concept of ''end-on insertion'', as differentiated from standard statistical equilibrium considerations, does not seem to be defensible on fundamental grounds, However, the equilibrium ''random pore'' treatment of Giddings yields relationships which are incompatible with the current results. The role of the dynamics of solute motion is discussed vis-a-vis hypothetical limitations of equilibrium models.